A while back I decided to make a temperature-controlled box for ales. I was hesitant to post until I fermented a couple in it. It works GREAT! I basically built a wooden frame out of wood and nailed insulation to it. I cut a little hole in the side and propped a little heater-fan from Lowes next to it.
I also took a mini-fridge and hooked it up to an appliance timer.
I calibrated the temperatures by using a cheap remote grill thermometer and putting it in a brew-bucket full of water and slowly adjusted the fan dial and spacing for the ale box and the appliance timer on the mini fridge over about a week until I sustained the temperature I wanted.
5 brews later, they hold their temperatures pretty steady. I don't even worry about the mini fridge, it hasn't dropped more than a degree since I calibrated it.
"There is an ancient Celtic axiom that says 'Good people drink good beer.' Which is true, then as now. Just look around you in any public barroom and you will quickly see: Bad people drink bad beer. Think about it."